1. Field of the Invention
The present invention relates to an additive block which may be coupled to a circuit breaker.
2. Description of the Prior Art
Such additive blocks are generally used as residual differential current protective devices, shunt releases or trips, voltage minima trips or trips of any other kind capable of causing opening of the circuit breaker from a given signal. They may also be used as auxiliary signalling devices signalling on the spot or at a distance tripping of the circuit breaker.
As is known, a circuit breaker generally comprises at least two separable contacts and a tripping mechanism comprising a storage spring and a tripping shaft, this mechanism being controlled to separate the contacts by a thermal release and/or a magnetic release capable of acting more especially in the case of a short circuit or an over current; it also comprises a manual or motorized means for resetting the tripping mechanism.
In known additive tripping blocks, the trip generally comprises a release electromagnet and a mechanical energy storage spring held under tension by a catch mechanism; the release electromagnet only therefore requires low power for releasing the mechanism. The mechanical energy released causes breaking of the circuit by acting on the release shaft of the circuit breaker through an appropriate connection mechanism. After each tripping operation, it is again obviously necessary to reset the catch mechanism of the additive block manually for example by means of a lever.
The circuit breaker and the additive block have a means accessible from the outside and allowing mechanical transmission of the tripping action, either in the additive block-circuit breaker direction with a trip addition or in the circuit breaker-additive block direction with a signalling addition.
Known embodiments of such additive blocks therefore require resetting which is either independent or dependent on resetting of the circuit breaker.
In the first case, it is necessary to design a free tripping mechanism independent of the resetting lever of the additive block so as not to temporarily cancel out the action of the trip during this operation when the circuit breaker has been previously reengaged. This design has the drawback of leading to an expensive construction.
In the second case, the distinction between a contact opening action caused by the tripping additive block and such an action proper to the circuit breaker is not correctly displayed for the user. Correlatively, this solution excludes the use of circuit breakers with automatic reset which would have the disadvantage of not allowing the user to question himself about the causes of the fault detected by the additive block.
The purpose of the present invention is more especially to overcome the above-mentioned drawbacks of known apparatus by creating an additive block which may be coupled to a circuit breaker and which only allows the circuit breaker to be reset by a conscious and voluntary action on the part of the user.